Over at the Presidential Power blog, David Doyle and I have reported a set of presidential power scores. These scores provide a continuous measure of the power of directly and indirectly presidents on a range from 0 (weak) to 1 (strong).

Scores for almost all semi-presidential countries are included. You can see how there is great variation in the presidential power scores across the set of countries with a semi-presidential constitution. For example, you can see how Austria and Iceland are constitutionally president-parliamentary, but have very low presidential power scores. You can also see that some parliamentary regimes with indirectly elected presidents have higher presidential power scores than some semi-presidential regimes with directly elected presidents.

This confirms the idea that the definition of regime types is first and foremost a taxonomical exercise. We can systematically capture differences between regime types by referring solely to the combination of a very small number of constitutional provisions. However, presidential power in practice depends on more than this combination of factors. So, while regimes types may provide a basic ordinal ranking of the relative strength of presidents – presidential and president-parliamentary countries do indeed tend to have stronger presidents than premier-presidential countries, which, in turn, do indeed tend to have stronger presidents than parliamentary countries – this ranking masks considerable variation in presidential power within each regime type.

So, if you wish to examine empirically the impact of presidential power on some or other outcome, then you have to make a decision. Is it better to test for the effect of regime types in the knowledge that this is operationalising a taxonomy that captures a fairly crude ordinal ranking of presidential power but that still might allow you to say something about the effect of presidentialism and president-parliamentarism relative to premier-presidentialism etc, or is it better to test for the effect of presidential power scores that capture such power continuously and in a much more fine-grained way, but that doesn’t allow you to say anything about regime types? It depends on your theory, I suppose.

If you do choose to to test for the effect of continuous presidential power scores, then we recommend that you use the scores in Doyle and Elgie.